1. Field of the Invention
This invention relates to a backhoe unit detachably attached to a backhoe mounting frame disposed on a tractor body rearwardly of a driver""s seat.
2. Description of the Related Art
Conventionally, this type of backhoe unit is applied to a tractor known as a TLB (tractor-loader-backhoe) having a loader attached to the front of a vehicle body and the backhoe unit to the rear of the vehicle body. In such a TLB, as disclosed in Japanese Patent Laying-Open Publication H10-7014 and U.S. Pat. No. 6,056,502, a backhoe mounting frame is disposed at the rear of a tractor body, and a base that supports a backhoe unit is detachably attached to this backhoe mounting frame. The base includes a pair of right and left stabilizers and a vertical swing axis about which a boom bracket is swingable. A boom assembly is attached to the boom bracket. The boom bracket is horizontally swung by a pair of right and left swing cylinders. The right and left swing cylinders are the trunnion type distributed laterally of the center of the base, and arranged to extend parallel to each other in the fore and aft direction of the tractor body. Thus, fore and aft long spaces are required for accommodating the swing cylinders. In addition, four hydraulic hoses are needed for the two swing cylinders requiring a large accommodation space also. The entire base therefore has in a large fore and aft dimension, resulting in an increased fore and aft length of the backhoe unit. The backhoe unit when attached imposes a considerable load on the tractor body.
The base of the backhoe unit has a footrest formed thereon, and a control column of rectangular cross section is disposed in a transversely middle position in a rearward region of the footrest. In a large TLB, spaces are formed between right and left rear wheel fenders and right and left sides of the control column of the backhoe unit attached, thereby providing walkthrough spaces for the driver which extend longitudinally of the tractor body.
However, in small and medium-size TLBs, only narrow spaces are formed between the right and left rear wheel fenders and the right and left sides of the control column. The control column must be disposed further rearward from the rear wheel fenders to produce walkthrough spaces extending transversely of the tractor body. This results in an increased distance from the rear end of the tractor body to the control column of the backhoe unit attached, thereby increasing the total length of the backhoe unit, particularly the fore and aft dimension of the base. The increased fore and aft dimension of the base is detrimental to the weight balance of the TLB.
The object of this invention is, starting from a backhoe unit including a base having engaging portions for connection to the backhoe mounting frame, a driver""s footrest and a control column disposed on the base, a vertical swing axis supported by the base, a boom bracket supported to be swingable about the vertical swing axis, and a boom assembly attached to the boom bracket, to overcome the disadvantages of the prior art noted above, and provide a compact backhoe unit that secures walkthrough spaces for the driver to climb up to and down from the footrest on the base with ease.
The above object is fulfilled, according to this invention, by a backhoe unit in which the boom bracket is swung horizontally by a single swing cylinder having one end thereof connected to the base through a first cylinder connecting portion, and the other end connected to the boom bracket through a second cylinder connecting portion, the swing cylinder being disposed in a lateral position of the base. With this construction, since the boom bracket of the backhoe unit is swung by a single swing cylinder, a construction relating to the swing cylinder is simplified, space may be reduced, and thus the base may have a reduced fore and aft dimension.
The swing cylinder may be placed to extend at an angle to a fore and aft direction of the tractor body. Then, the swing cylinder occupies a reduced fore and aft length, thereby reducing the fore and aft dimension of the base. This contributes toward a reduction in the load of the backhoe unit applied to the tractor body.
The swing cylinder is subjected to a heavy load. It is therefore preferable to support the swing cylinder by a strong portion of the base. As a specific measure therefor, it is proposed here that the engaging portions include a pair of right and left upper engaging portions and a lower engaging portion, the first cylinder connecting portion being disposed in a region substantially between the upper engaging portions and the lower engaging portion.
To achieve the above object, this invention proposes to limit an angle of swinging of the boom bracket by the swing cylinder to be smaller than 90 degrees. This is based on breaking of the fixed idea that the boom assembly must be horizontally swung 90 degrees right and left to transport soil, stone and the like with the bucket of the boom assembly. That is, by reducing the swing angle, a reduction is achieved in the distance between the vertical swing axis and backhoe mounting unit. It is extremely rate to swing the boom assembly 90 degrees to the right or left. There is hardly any disadvantage in performing ordinary operations if the swing angle of the boom bracket is limited to be smaller than 90 degrees. A simple form for limiting the swing angle reliably may be a pair of right and left stoppers disposed on the backhoe mounting frame for contacting the boom bracket. These stoppers may be disposed on the backhoe mounting frame.
The boom approaches the control column when the boom assembly is swung upward. In a preferred embodiment of this invention, the control column has a casing defining an opening in a lower rear portion thereof for permitting entry of an arm cylinder support of the boom assembly when the boom assembly swings upward by a maximum angle. This construction further reduces the fore and aft dimension from the control column to the vertical swing axis, and hence the fore and aft length of the backhoe unit.
As another measure for reducing the fore and aft dimension from the control column to the vertical swing axis, it is proposed that the distance from a rear surface of the casing to the vertical swing axis is smaller than a half of a maximum width of the boom assembly. The fore and aft dimension from the control column to the vertical swing axis may be reduced also where the footrest includes right and left portions located adjacent rear ends of right and left rear wheel fenders of the tractor, and a middle portion projecting forwardly of the rear ends of the right and left rear wheel fenders.
In a preferred embodiment of this invention, the engaging portions include a pair of right and left upper engaging portions and a lower engaging portion, and each of the upper engaging portions includes a pair of upper and lower mount holders vertically pivotably supported by pivotal supports to be forwardly openable and closable for approaching, from behind, an upper coupling attached to the backhoe mounting frame, and removably engaging the upper coupling from radially outward directions, and a retaining member movable, from behind, into a space between the mount holders and rearwardly of the pivotal supports for locking the mount holders against pivotal movement, the upper and lower mount holders being formed asymmetrical and the retaining member being inclined rearward and downward, thereby allowing the retaining member to extend under the footrest. This construction allows the footrest to be disposed close to the rear end of the tractor and to have an increased area.
The boom bracket may have a lower end thereof substantially level with the engaging portions. Thus, the base may be disposed in the lowest possible level to stabilize the weight balance of the backhoe unit.
To fulfill the foregoing object of this invention, it is also proposed that a walkthrough space is formed on the footrest to extend obliquely rearward from a rear position of the driver""s seat.
Though a sufficient walkthrough space is formed for the driver, this construction reduces the fore and aft dimension from the rear end of the tractor body to the control column, contributing to making the base of the backhoe unit compact.
Further, the control column may have a casing with a front surface thereof smaller in width than a rear surface, and right and left sides inclined rearwardly and outwardly from the front surface. Thus, the fore and aft dimension from the rear end of the tractor body to the control column may be reduced while securing the large walkthrough space.
In one preferred embodiment of this invention, the footrest includes a pair of right and left foot supports diverging rearward for the driver""s feet to be placed at opposite sides of the control column, and a passage portion extending between heel ends of the foot supports forwardly of the control column for enabling movement of the driver""s feet. With this construction also, the fore and aft dimension from the rear end of the tractor body to the control column may be reduced while securing a sufficient space for the driver.
The footrest may include foot stoppers formed laterally of front edges thereof. Then, a projection of the feet from the footrest may be restricted even though the fore and aft dimension from the rear end of the tractor to the control column is reduced.
It is also advantageous to employ a construction in which the footrest is approximately channel-shaped opening rearward in plan view, the control column being trapezoidal, diverging rearward in plan view, and being disposed in a rearwardly opening portion of the footrest.
Further, the casing of the control column may house control valves for controlling the swing cylinder and the boom assembly, the control valves being operable by control levers arranged above the control valves. Then a free space is provided outside the control column, and no obstructive components are present around the driver""s feet.
Other features and advantages of this invention will be apparent from the following description of the embodiment to be taken with reference to the drawings.